Pre-cementation of deep shaft
Pre-cementation or pre-grouting of deep shafts in South Africa is an established technique to improve safety and reduce water ingress during shaft sinking. The recent completion of several pre-cementation projects for shafts deeper than 1000m has once again highlighted the effectiveness of pre-grouting of shafts utilizing deep slimline boreholes and incorporating wireline technique for drilling and conventional deep borehole grouting techniques for pre-cementation.
Increase the safety of shaft sinking operation
Minimize water and gas inflow during shaft sinking
Minimize the time lost due to additional grouting operations during sinking of the shaft and hence minimize costly delays and standing time of shaft sinking crews and equipment.
Provide detailed information of the geology of the proposed shaft site. Informations on anomalies, dykes, faults as well as reef (gold bearing conglomerates) intersections can be obtained from the evaluation of cores of the pre-cementation boreholes.
Provide improved rock strength for excavations in the immediate vicinity of the shaft area.
The paper describes pre-cementation techniques recently applied successfully from surface and some conclusions drawn for further considerations.
KeywordsDrilling Ordinary Portland Cement Water Inrush Costly Delay Cement Slurry
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